| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| // |
| // For information about UTF-8 strings in Go, see https://blog.golang.org/strings. |
| package strings |
| |
| import ( |
| "internal/bytealg" |
| "unicode" |
| "unicode/utf8" |
| ) |
| |
| const maxInt = int(^uint(0) >> 1) |
| |
| // explode splits s into a slice of UTF-8 strings, |
| // one string per Unicode character up to a maximum of n (n < 0 means no limit). |
| // Invalid UTF-8 bytes are sliced individually. |
| func explode(s string, n int) []string { |
| l := utf8.RuneCountInString(s) |
| if n < 0 || n > l { |
| n = l |
| } |
| a := make([]string, n) |
| for i := 0; i < n-1; i++ { |
| _, size := utf8.DecodeRuneInString(s) |
| a[i] = s[:size] |
| s = s[size:] |
| } |
| if n > 0 { |
| a[n-1] = s |
| } |
| return a |
| } |
| |
| // Count counts the number of non-overlapping instances of substr in s. |
| // If substr is an empty string, Count returns 1 + the number of Unicode code points in s. |
| func Count(s, substr string) int { |
| // special case |
| if len(substr) == 0 { |
| return utf8.RuneCountInString(s) + 1 |
| } |
| if len(substr) == 1 { |
| return bytealg.CountString(s, substr[0]) |
| } |
| n := 0 |
| for { |
| i := Index(s, substr) |
| if i == -1 { |
| return n |
| } |
| n++ |
| s = s[i+len(substr):] |
| } |
| } |
| |
| // Contains reports whether substr is within s. |
| func Contains(s, substr string) bool { |
| return Index(s, substr) >= 0 |
| } |
| |
| // ContainsAny reports whether any Unicode code points in chars are within s. |
| func ContainsAny(s, chars string) bool { |
| return IndexAny(s, chars) >= 0 |
| } |
| |
| // ContainsRune reports whether the Unicode code point r is within s. |
| func ContainsRune(s string, r rune) bool { |
| return IndexRune(s, r) >= 0 |
| } |
| |
| // ContainsFunc reports whether any Unicode code points r within s satisfy f(r). |
| func ContainsFunc(s string, f func(rune) bool) bool { |
| return IndexFunc(s, f) >= 0 |
| } |
| |
| // LastIndex returns the index of the last instance of substr in s, or -1 if substr is not present in s. |
| func LastIndex(s, substr string) int { |
| n := len(substr) |
| switch { |
| case n == 0: |
| return len(s) |
| case n == 1: |
| return LastIndexByte(s, substr[0]) |
| case n == len(s): |
| if substr == s { |
| return 0 |
| } |
| return -1 |
| case n > len(s): |
| return -1 |
| } |
| // Rabin-Karp search from the end of the string |
| hashss, pow := bytealg.HashStrRev(substr) |
| last := len(s) - n |
| var h uint32 |
| for i := len(s) - 1; i >= last; i-- { |
| h = h*bytealg.PrimeRK + uint32(s[i]) |
| } |
| if h == hashss && s[last:] == substr { |
| return last |
| } |
| for i := last - 1; i >= 0; i-- { |
| h *= bytealg.PrimeRK |
| h += uint32(s[i]) |
| h -= pow * uint32(s[i+n]) |
| if h == hashss && s[i:i+n] == substr { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // IndexByte returns the index of the first instance of c in s, or -1 if c is not present in s. |
| func IndexByte(s string, c byte) int { |
| return bytealg.IndexByteString(s, c) |
| } |
| |
| // IndexRune returns the index of the first instance of the Unicode code point |
| // r, or -1 if rune is not present in s. |
| // If r is utf8.RuneError, it returns the first instance of any |
| // invalid UTF-8 byte sequence. |
| func IndexRune(s string, r rune) int { |
| switch { |
| case 0 <= r && r < utf8.RuneSelf: |
| return IndexByte(s, byte(r)) |
| case r == utf8.RuneError: |
| for i, r := range s { |
| if r == utf8.RuneError { |
| return i |
| } |
| } |
| return -1 |
| case !utf8.ValidRune(r): |
| return -1 |
| default: |
| return Index(s, string(r)) |
| } |
| } |
| |
| // IndexAny returns the index of the first instance of any Unicode code point |
| // from chars in s, or -1 if no Unicode code point from chars is present in s. |
| func IndexAny(s, chars string) int { |
| if chars == "" { |
| // Avoid scanning all of s. |
| return -1 |
| } |
| if len(chars) == 1 { |
| // Avoid scanning all of s. |
| r := rune(chars[0]) |
| if r >= utf8.RuneSelf { |
| r = utf8.RuneError |
| } |
| return IndexRune(s, r) |
| } |
| if len(s) > 8 { |
| if as, isASCII := makeASCIISet(chars); isASCII { |
| for i := 0; i < len(s); i++ { |
| if as.contains(s[i]) { |
| return i |
| } |
| } |
| return -1 |
| } |
| } |
| for i, c := range s { |
| if IndexRune(chars, c) >= 0 { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // LastIndexAny returns the index of the last instance of any Unicode code |
| // point from chars in s, or -1 if no Unicode code point from chars is |
| // present in s. |
| func LastIndexAny(s, chars string) int { |
| if chars == "" { |
| // Avoid scanning all of s. |
| return -1 |
| } |
| if len(s) == 1 { |
| rc := rune(s[0]) |
| if rc >= utf8.RuneSelf { |
| rc = utf8.RuneError |
| } |
| if IndexRune(chars, rc) >= 0 { |
| return 0 |
| } |
| return -1 |
| } |
| if len(s) > 8 { |
| if as, isASCII := makeASCIISet(chars); isASCII { |
| for i := len(s) - 1; i >= 0; i-- { |
| if as.contains(s[i]) { |
| return i |
| } |
| } |
| return -1 |
| } |
| } |
| if len(chars) == 1 { |
| rc := rune(chars[0]) |
| if rc >= utf8.RuneSelf { |
| rc = utf8.RuneError |
| } |
| for i := len(s); i > 0; { |
| r, size := utf8.DecodeLastRuneInString(s[:i]) |
| i -= size |
| if rc == r { |
| return i |
| } |
| } |
| return -1 |
| } |
| for i := len(s); i > 0; { |
| r, size := utf8.DecodeLastRuneInString(s[:i]) |
| i -= size |
| if IndexRune(chars, r) >= 0 { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s. |
| func LastIndexByte(s string, c byte) int { |
| for i := len(s) - 1; i >= 0; i-- { |
| if s[i] == c { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // Generic split: splits after each instance of sep, |
| // including sepSave bytes of sep in the subarrays. |
| func genSplit(s, sep string, sepSave, n int) []string { |
| if n == 0 { |
| return nil |
| } |
| if sep == "" { |
| return explode(s, n) |
| } |
| if n < 0 { |
| n = Count(s, sep) + 1 |
| } |
| |
| if n > len(s)+1 { |
| n = len(s) + 1 |
| } |
| a := make([]string, n) |
| n-- |
| i := 0 |
| for i < n { |
| m := Index(s, sep) |
| if m < 0 { |
| break |
| } |
| a[i] = s[:m+sepSave] |
| s = s[m+len(sep):] |
| i++ |
| } |
| a[i] = s |
| return a[:i+1] |
| } |
| |
| // SplitN slices s into substrings separated by sep and returns a slice of |
| // the substrings between those separators. |
| // |
| // The count determines the number of substrings to return: |
| // |
| // n > 0: at most n substrings; the last substring will be the unsplit remainder. |
| // n == 0: the result is nil (zero substrings) |
| // n < 0: all substrings |
| // |
| // Edge cases for s and sep (for example, empty strings) are handled |
| // as described in the documentation for Split. |
| // |
| // To split around the first instance of a separator, see Cut. |
| func SplitN(s, sep string, n int) []string { return genSplit(s, sep, 0, n) } |
| |
| // SplitAfterN slices s into substrings after each instance of sep and |
| // returns a slice of those substrings. |
| // |
| // The count determines the number of substrings to return: |
| // |
| // n > 0: at most n substrings; the last substring will be the unsplit remainder. |
| // n == 0: the result is nil (zero substrings) |
| // n < 0: all substrings |
| // |
| // Edge cases for s and sep (for example, empty strings) are handled |
| // as described in the documentation for SplitAfter. |
| func SplitAfterN(s, sep string, n int) []string { |
| return genSplit(s, sep, len(sep), n) |
| } |
| |
| // Split slices s into all substrings separated by sep and returns a slice of |
| // the substrings between those separators. |
| // |
| // If s does not contain sep and sep is not empty, Split returns a |
| // slice of length 1 whose only element is s. |
| // |
| // If sep is empty, Split splits after each UTF-8 sequence. If both s |
| // and sep are empty, Split returns an empty slice. |
| // |
| // It is equivalent to SplitN with a count of -1. |
| // |
| // To split around the first instance of a separator, see Cut. |
| func Split(s, sep string) []string { return genSplit(s, sep, 0, -1) } |
| |
| // SplitAfter slices s into all substrings after each instance of sep and |
| // returns a slice of those substrings. |
| // |
| // If s does not contain sep and sep is not empty, SplitAfter returns |
| // a slice of length 1 whose only element is s. |
| // |
| // If sep is empty, SplitAfter splits after each UTF-8 sequence. If |
| // both s and sep are empty, SplitAfter returns an empty slice. |
| // |
| // It is equivalent to SplitAfterN with a count of -1. |
| func SplitAfter(s, sep string) []string { |
| return genSplit(s, sep, len(sep), -1) |
| } |
| |
| var asciiSpace = [256]uint8{'\t': 1, '\n': 1, '\v': 1, '\f': 1, '\r': 1, ' ': 1} |
| |
| // Fields splits the string s around each instance of one or more consecutive white space |
| // characters, as defined by unicode.IsSpace, returning a slice of substrings of s or an |
| // empty slice if s contains only white space. |
| func Fields(s string) []string { |
| // First count the fields. |
| // This is an exact count if s is ASCII, otherwise it is an approximation. |
| n := 0 |
| wasSpace := 1 |
| // setBits is used to track which bits are set in the bytes of s. |
| setBits := uint8(0) |
| for i := 0; i < len(s); i++ { |
| r := s[i] |
| setBits |= r |
| isSpace := int(asciiSpace[r]) |
| n += wasSpace & ^isSpace |
| wasSpace = isSpace |
| } |
| |
| if setBits >= utf8.RuneSelf { |
| // Some runes in the input string are not ASCII. |
| return FieldsFunc(s, unicode.IsSpace) |
| } |
| // ASCII fast path |
| a := make([]string, n) |
| na := 0 |
| fieldStart := 0 |
| i := 0 |
| // Skip spaces in the front of the input. |
| for i < len(s) && asciiSpace[s[i]] != 0 { |
| i++ |
| } |
| fieldStart = i |
| for i < len(s) { |
| if asciiSpace[s[i]] == 0 { |
| i++ |
| continue |
| } |
| a[na] = s[fieldStart:i] |
| na++ |
| i++ |
| // Skip spaces in between fields. |
| for i < len(s) && asciiSpace[s[i]] != 0 { |
| i++ |
| } |
| fieldStart = i |
| } |
| if fieldStart < len(s) { // Last field might end at EOF. |
| a[na] = s[fieldStart:] |
| } |
| return a |
| } |
| |
| // FieldsFunc splits the string s at each run of Unicode code points c satisfying f(c) |
| // and returns an array of slices of s. If all code points in s satisfy f(c) or the |
| // string is empty, an empty slice is returned. |
| // |
| // FieldsFunc makes no guarantees about the order in which it calls f(c) |
| // and assumes that f always returns the same value for a given c. |
| func FieldsFunc(s string, f func(rune) bool) []string { |
| // A span is used to record a slice of s of the form s[start:end]. |
| // The start index is inclusive and the end index is exclusive. |
| type span struct { |
| start int |
| end int |
| } |
| spans := make([]span, 0, 32) |
| |
| // Find the field start and end indices. |
| // Doing this in a separate pass (rather than slicing the string s |
| // and collecting the result substrings right away) is significantly |
| // more efficient, possibly due to cache effects. |
| start := -1 // valid span start if >= 0 |
| for end, rune := range s { |
| if f(rune) { |
| if start >= 0 { |
| spans = append(spans, span{start, end}) |
| // Set start to a negative value. |
| // Note: using -1 here consistently and reproducibly |
| // slows down this code by a several percent on amd64. |
| start = ^start |
| } |
| } else { |
| if start < 0 { |
| start = end |
| } |
| } |
| } |
| |
| // Last field might end at EOF. |
| if start >= 0 { |
| spans = append(spans, span{start, len(s)}) |
| } |
| |
| // Create strings from recorded field indices. |
| a := make([]string, len(spans)) |
| for i, span := range spans { |
| a[i] = s[span.start:span.end] |
| } |
| |
| return a |
| } |
| |
| // Join concatenates the elements of its first argument to create a single string. The separator |
| // string sep is placed between elements in the resulting string. |
| func Join(elems []string, sep string) string { |
| switch len(elems) { |
| case 0: |
| return "" |
| case 1: |
| return elems[0] |
| } |
| |
| var n int |
| if len(sep) > 0 { |
| if len(sep) >= maxInt/(len(elems)-1) { |
| panic("strings: Join output length overflow") |
| } |
| n += len(sep) * (len(elems) - 1) |
| } |
| for _, elem := range elems { |
| if len(elem) > maxInt-n { |
| panic("strings: Join output length overflow") |
| } |
| n += len(elem) |
| } |
| |
| var b Builder |
| b.Grow(n) |
| b.WriteString(elems[0]) |
| for _, s := range elems[1:] { |
| b.WriteString(sep) |
| b.WriteString(s) |
| } |
| return b.String() |
| } |
| |
| // HasPrefix tests whether the string s begins with prefix. |
| func HasPrefix(s, prefix string) bool { |
| return len(s) >= len(prefix) && s[0:len(prefix)] == prefix |
| } |
| |
| // HasSuffix tests whether the string s ends with suffix. |
| func HasSuffix(s, suffix string) bool { |
| return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix |
| } |
| |
| // Map returns a copy of the string s with all its characters modified |
| // according to the mapping function. If mapping returns a negative value, the character is |
| // dropped from the string with no replacement. |
| func Map(mapping func(rune) rune, s string) string { |
| // In the worst case, the string can grow when mapped, making |
| // things unpleasant. But it's so rare we barge in assuming it's |
| // fine. It could also shrink but that falls out naturally. |
| |
| // The output buffer b is initialized on demand, the first |
| // time a character differs. |
| var b Builder |
| |
| for i, c := range s { |
| r := mapping(c) |
| if r == c && c != utf8.RuneError { |
| continue |
| } |
| |
| var width int |
| if c == utf8.RuneError { |
| c, width = utf8.DecodeRuneInString(s[i:]) |
| if width != 1 && r == c { |
| continue |
| } |
| } else { |
| width = utf8.RuneLen(c) |
| } |
| |
| b.Grow(len(s) + utf8.UTFMax) |
| b.WriteString(s[:i]) |
| if r >= 0 { |
| b.WriteRune(r) |
| } |
| |
| s = s[i+width:] |
| break |
| } |
| |
| // Fast path for unchanged input |
| if b.Cap() == 0 { // didn't call b.Grow above |
| return s |
| } |
| |
| for _, c := range s { |
| r := mapping(c) |
| |
| if r >= 0 { |
| // common case |
| // Due to inlining, it is more performant to determine if WriteByte should be |
| // invoked rather than always call WriteRune |
| if r < utf8.RuneSelf { |
| b.WriteByte(byte(r)) |
| } else { |
| // r is not a ASCII rune. |
| b.WriteRune(r) |
| } |
| } |
| } |
| |
| return b.String() |
| } |
| |
| // Repeat returns a new string consisting of count copies of the string s. |
| // |
| // It panics if count is negative or if the result of (len(s) * count) |
| // overflows. |
| func Repeat(s string, count int) string { |
| switch count { |
| case 0: |
| return "" |
| case 1: |
| return s |
| } |
| |
| // Since we cannot return an error on overflow, |
| // we should panic if the repeat will generate an overflow. |
| // See golang.org/issue/16237. |
| if count < 0 { |
| panic("strings: negative Repeat count") |
| } |
| if len(s) >= maxInt/count { |
| panic("strings: Repeat output length overflow") |
| } |
| n := len(s) * count |
| |
| if len(s) == 0 { |
| return "" |
| } |
| |
| // Past a certain chunk size it is counterproductive to use |
| // larger chunks as the source of the write, as when the source |
| // is too large we are basically just thrashing the CPU D-cache. |
| // So if the result length is larger than an empirically-found |
| // limit (8KB), we stop growing the source string once the limit |
| // is reached and keep reusing the same source string - that |
| // should therefore be always resident in the L1 cache - until we |
| // have completed the construction of the result. |
| // This yields significant speedups (up to +100%) in cases where |
| // the result length is large (roughly, over L2 cache size). |
| const chunkLimit = 8 * 1024 |
| chunkMax := n |
| if n > chunkLimit { |
| chunkMax = chunkLimit / len(s) * len(s) |
| if chunkMax == 0 { |
| chunkMax = len(s) |
| } |
| } |
| |
| var b Builder |
| b.Grow(n) |
| b.WriteString(s) |
| for b.Len() < n { |
| chunk := n - b.Len() |
| if chunk > b.Len() { |
| chunk = b.Len() |
| } |
| if chunk > chunkMax { |
| chunk = chunkMax |
| } |
| b.WriteString(b.String()[:chunk]) |
| } |
| return b.String() |
| } |
| |
| // ToUpper returns s with all Unicode letters mapped to their upper case. |
| func ToUpper(s string) string { |
| isASCII, hasLower := true, false |
| for i := 0; i < len(s); i++ { |
| c := s[i] |
| if c >= utf8.RuneSelf { |
| isASCII = false |
| break |
| } |
| hasLower = hasLower || ('a' <= c && c <= 'z') |
| } |
| |
| if isASCII { // optimize for ASCII-only strings. |
| if !hasLower { |
| return s |
| } |
| var ( |
| b Builder |
| pos int |
| ) |
| b.Grow(len(s)) |
| for i := 0; i < len(s); i++ { |
| c := s[i] |
| if 'a' <= c && c <= 'z' { |
| c -= 'a' - 'A' |
| if pos < i { |
| b.WriteString(s[pos:i]) |
| } |
| b.WriteByte(c) |
| pos = i + 1 |
| } |
| } |
| if pos < len(s) { |
| b.WriteString(s[pos:]) |
| } |
| return b.String() |
| } |
| return Map(unicode.ToUpper, s) |
| } |
| |
| // ToLower returns s with all Unicode letters mapped to their lower case. |
| func ToLower(s string) string { |
| isASCII, hasUpper := true, false |
| for i := 0; i < len(s); i++ { |
| c := s[i] |
| if c >= utf8.RuneSelf { |
| isASCII = false |
| break |
| } |
| hasUpper = hasUpper || ('A' <= c && c <= 'Z') |
| } |
| |
| if isASCII { // optimize for ASCII-only strings. |
| if !hasUpper { |
| return s |
| } |
| var ( |
| b Builder |
| pos int |
| ) |
| b.Grow(len(s)) |
| for i := 0; i < len(s); i++ { |
| c := s[i] |
| if 'A' <= c && c <= 'Z' { |
| c += 'a' - 'A' |
| if pos < i { |
| b.WriteString(s[pos:i]) |
| } |
| b.WriteByte(c) |
| pos = i + 1 |
| } |
| } |
| if pos < len(s) { |
| b.WriteString(s[pos:]) |
| } |
| return b.String() |
| } |
| return Map(unicode.ToLower, s) |
| } |
| |
| // ToTitle returns a copy of the string s with all Unicode letters mapped to |
| // their Unicode title case. |
| func ToTitle(s string) string { return Map(unicode.ToTitle, s) } |
| |
| // ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their |
| // upper case using the case mapping specified by c. |
| func ToUpperSpecial(c unicode.SpecialCase, s string) string { |
| return Map(c.ToUpper, s) |
| } |
| |
| // ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their |
| // lower case using the case mapping specified by c. |
| func ToLowerSpecial(c unicode.SpecialCase, s string) string { |
| return Map(c.ToLower, s) |
| } |
| |
| // ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their |
| // Unicode title case, giving priority to the special casing rules. |
| func ToTitleSpecial(c unicode.SpecialCase, s string) string { |
| return Map(c.ToTitle, s) |
| } |
| |
| // ToValidUTF8 returns a copy of the string s with each run of invalid UTF-8 byte sequences |
| // replaced by the replacement string, which may be empty. |
| func ToValidUTF8(s, replacement string) string { |
| var b Builder |
| |
| for i, c := range s { |
| if c != utf8.RuneError { |
| continue |
| } |
| |
| _, wid := utf8.DecodeRuneInString(s[i:]) |
| if wid == 1 { |
| b.Grow(len(s) + len(replacement)) |
| b.WriteString(s[:i]) |
| s = s[i:] |
| break |
| } |
| } |
| |
| // Fast path for unchanged input |
| if b.Cap() == 0 { // didn't call b.Grow above |
| return s |
| } |
| |
| invalid := false // previous byte was from an invalid UTF-8 sequence |
| for i := 0; i < len(s); { |
| c := s[i] |
| if c < utf8.RuneSelf { |
| i++ |
| invalid = false |
| b.WriteByte(c) |
| continue |
| } |
| _, wid := utf8.DecodeRuneInString(s[i:]) |
| if wid == 1 { |
| i++ |
| if !invalid { |
| invalid = true |
| b.WriteString(replacement) |
| } |
| continue |
| } |
| invalid = false |
| b.WriteString(s[i : i+wid]) |
| i += wid |
| } |
| |
| return b.String() |
| } |
| |
| // isSeparator reports whether the rune could mark a word boundary. |
| // TODO: update when package unicode captures more of the properties. |
| func isSeparator(r rune) bool { |
| // ASCII alphanumerics and underscore are not separators |
| if r <= 0x7F { |
| switch { |
| case '0' <= r && r <= '9': |
| return false |
| case 'a' <= r && r <= 'z': |
| return false |
| case 'A' <= r && r <= 'Z': |
| return false |
| case r == '_': |
| return false |
| } |
| return true |
| } |
| // Letters and digits are not separators |
| if unicode.IsLetter(r) || unicode.IsDigit(r) { |
| return false |
| } |
| // Otherwise, all we can do for now is treat spaces as separators. |
| return unicode.IsSpace(r) |
| } |
| |
| // Title returns a copy of the string s with all Unicode letters that begin words |
| // mapped to their Unicode title case. |
| // |
| // Deprecated: The rule Title uses for word boundaries does not handle Unicode |
| // punctuation properly. Use golang.org/x/text/cases instead. |
| func Title(s string) string { |
| // Use a closure here to remember state. |
| // Hackish but effective. Depends on Map scanning in order and calling |
| // the closure once per rune. |
| prev := ' ' |
| return Map( |
| func(r rune) rune { |
| if isSeparator(prev) { |
| prev = r |
| return unicode.ToTitle(r) |
| } |
| prev = r |
| return r |
| }, |
| s) |
| } |
| |
| // TrimLeftFunc returns a slice of the string s with all leading |
| // Unicode code points c satisfying f(c) removed. |
| func TrimLeftFunc(s string, f func(rune) bool) string { |
| i := indexFunc(s, f, false) |
| if i == -1 { |
| return "" |
| } |
| return s[i:] |
| } |
| |
| // TrimRightFunc returns a slice of the string s with all trailing |
| // Unicode code points c satisfying f(c) removed. |
| func TrimRightFunc(s string, f func(rune) bool) string { |
| i := lastIndexFunc(s, f, false) |
| if i >= 0 && s[i] >= utf8.RuneSelf { |
| _, wid := utf8.DecodeRuneInString(s[i:]) |
| i += wid |
| } else { |
| i++ |
| } |
| return s[0:i] |
| } |
| |
| // TrimFunc returns a slice of the string s with all leading |
| // and trailing Unicode code points c satisfying f(c) removed. |
| func TrimFunc(s string, f func(rune) bool) string { |
| return TrimRightFunc(TrimLeftFunc(s, f), f) |
| } |
| |
| // IndexFunc returns the index into s of the first Unicode |
| // code point satisfying f(c), or -1 if none do. |
| func IndexFunc(s string, f func(rune) bool) int { |
| return indexFunc(s, f, true) |
| } |
| |
| // LastIndexFunc returns the index into s of the last |
| // Unicode code point satisfying f(c), or -1 if none do. |
| func LastIndexFunc(s string, f func(rune) bool) int { |
| return lastIndexFunc(s, f, true) |
| } |
| |
| // indexFunc is the same as IndexFunc except that if |
| // truth==false, the sense of the predicate function is |
| // inverted. |
| func indexFunc(s string, f func(rune) bool, truth bool) int { |
| for i, r := range s { |
| if f(r) == truth { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // lastIndexFunc is the same as LastIndexFunc except that if |
| // truth==false, the sense of the predicate function is |
| // inverted. |
| func lastIndexFunc(s string, f func(rune) bool, truth bool) int { |
| for i := len(s); i > 0; { |
| r, size := utf8.DecodeLastRuneInString(s[0:i]) |
| i -= size |
| if f(r) == truth { |
| return i |
| } |
| } |
| return -1 |
| } |
| |
| // asciiSet is a 32-byte value, where each bit represents the presence of a |
| // given ASCII character in the set. The 128-bits of the lower 16 bytes, |
| // starting with the least-significant bit of the lowest word to the |
| // most-significant bit of the highest word, map to the full range of all |
| // 128 ASCII characters. The 128-bits of the upper 16 bytes will be zeroed, |
| // ensuring that any non-ASCII character will be reported as not in the set. |
| // This allocates a total of 32 bytes even though the upper half |
| // is unused to avoid bounds checks in asciiSet.contains. |
| type asciiSet [8]uint32 |
| |
| // makeASCIISet creates a set of ASCII characters and reports whether all |
| // characters in chars are ASCII. |
| func makeASCIISet(chars string) (as asciiSet, ok bool) { |
| for i := 0; i < len(chars); i++ { |
| c := chars[i] |
| if c >= utf8.RuneSelf { |
| return as, false |
| } |
| as[c/32] |= 1 << (c % 32) |
| } |
| return as, true |
| } |
| |
| // contains reports whether c is inside the set. |
| func (as *asciiSet) contains(c byte) bool { |
| return (as[c/32] & (1 << (c % 32))) != 0 |
| } |
| |
| // Trim returns a slice of the string s with all leading and |
| // trailing Unicode code points contained in cutset removed. |
| func Trim(s, cutset string) string { |
| if s == "" || cutset == "" { |
| return s |
| } |
| if len(cutset) == 1 && cutset[0] < utf8.RuneSelf { |
| return trimLeftByte(trimRightByte(s, cutset[0]), cutset[0]) |
| } |
| if as, ok := makeASCIISet(cutset); ok { |
| return trimLeftASCII(trimRightASCII(s, &as), &as) |
| } |
| return trimLeftUnicode(trimRightUnicode(s, cutset), cutset) |
| } |
| |
| // TrimLeft returns a slice of the string s with all leading |
| // Unicode code points contained in cutset removed. |
| // |
| // To remove a prefix, use TrimPrefix instead. |
| func TrimLeft(s, cutset string) string { |
| if s == "" || cutset == "" { |
| return s |
| } |
| if len(cutset) == 1 && cutset[0] < utf8.RuneSelf { |
| return trimLeftByte(s, cutset[0]) |
| } |
| if as, ok := makeASCIISet(cutset); ok { |
| return trimLeftASCII(s, &as) |
| } |
| return trimLeftUnicode(s, cutset) |
| } |
| |
| func trimLeftByte(s string, c byte) string { |
| for len(s) > 0 && s[0] == c { |
| s = s[1:] |
| } |
| return s |
| } |
| |
| func trimLeftASCII(s string, as *asciiSet) string { |
| for len(s) > 0 { |
| if !as.contains(s[0]) { |
| break |
| } |
| s = s[1:] |
| } |
| return s |
| } |
| |
| func trimLeftUnicode(s, cutset string) string { |
| for len(s) > 0 { |
| r, n := rune(s[0]), 1 |
| if r >= utf8.RuneSelf { |
| r, n = utf8.DecodeRuneInString(s) |
| } |
| if !ContainsRune(cutset, r) { |
| break |
| } |
| s = s[n:] |
| } |
| return s |
| } |
| |
| // TrimRight returns a slice of the string s, with all trailing |
| // Unicode code points contained in cutset removed. |
| // |
| // To remove a suffix, use TrimSuffix instead. |
| func TrimRight(s, cutset string) string { |
| if s == "" || cutset == "" { |
| return s |
| } |
| if len(cutset) == 1 && cutset[0] < utf8.RuneSelf { |
| return trimRightByte(s, cutset[0]) |
| } |
| if as, ok := makeASCIISet(cutset); ok { |
| return trimRightASCII(s, &as) |
| } |
| return trimRightUnicode(s, cutset) |
| } |
| |
| func trimRightByte(s string, c byte) string { |
| for len(s) > 0 && s[len(s)-1] == c { |
| s = s[:len(s)-1] |
| } |
| return s |
| } |
| |
| func trimRightASCII(s string, as *asciiSet) string { |
| for len(s) > 0 { |
| if !as.contains(s[len(s)-1]) { |
| break |
| } |
| s = s[:len(s)-1] |
| } |
| return s |
| } |
| |
| func trimRightUnicode(s, cutset string) string { |
| for len(s) > 0 { |
| r, n := rune(s[len(s)-1]), 1 |
| if r >= utf8.RuneSelf { |
| r, n = utf8.DecodeLastRuneInString(s) |
| } |
| if !ContainsRune(cutset, r) { |
| break |
| } |
| s = s[:len(s)-n] |
| } |
| return s |
| } |
| |
| // TrimSpace returns a slice of the string s, with all leading |
| // and trailing white space removed, as defined by Unicode. |
| func TrimSpace(s string) string { |
| // Fast path for ASCII: look for the first ASCII non-space byte |
| start := 0 |
| for ; start < len(s); start++ { |
| c := s[start] |
| if c >= utf8.RuneSelf { |
| // If we run into a non-ASCII byte, fall back to the |
| // slower unicode-aware method on the remaining bytes |
| return TrimFunc(s[start:], unicode.IsSpace) |
| } |
| if asciiSpace[c] == 0 { |
| break |
| } |
| } |
| |
| // Now look for the first ASCII non-space byte from the end |
| stop := len(s) |
| for ; stop > start; stop-- { |
| c := s[stop-1] |
| if c >= utf8.RuneSelf { |
| // start has been already trimmed above, should trim end only |
| return TrimRightFunc(s[start:stop], unicode.IsSpace) |
| } |
| if asciiSpace[c] == 0 { |
| break |
| } |
| } |
| |
| // At this point s[start:stop] starts and ends with an ASCII |
| // non-space bytes, so we're done. Non-ASCII cases have already |
| // been handled above. |
| return s[start:stop] |
| } |
| |
| // TrimPrefix returns s without the provided leading prefix string. |
| // If s doesn't start with prefix, s is returned unchanged. |
| func TrimPrefix(s, prefix string) string { |
| if HasPrefix(s, prefix) { |
| return s[len(prefix):] |
| } |
| return s |
| } |
| |
| // TrimSuffix returns s without the provided trailing suffix string. |
| // If s doesn't end with suffix, s is returned unchanged. |
| func TrimSuffix(s, suffix string) string { |
| if HasSuffix(s, suffix) { |
| return s[:len(s)-len(suffix)] |
| } |
| return s |
| } |
| |
| // Replace returns a copy of the string s with the first n |
| // non-overlapping instances of old replaced by new. |
| // If old is empty, it matches at the beginning of the string |
| // and after each UTF-8 sequence, yielding up to k+1 replacements |
| // for a k-rune string. |
| // If n < 0, there is no limit on the number of replacements. |
| func Replace(s, old, new string, n int) string { |
| if old == new || n == 0 { |
| return s // avoid allocation |
| } |
| |
| // Compute number of replacements. |
| if m := Count(s, old); m == 0 { |
| return s // avoid allocation |
| } else if n < 0 || m < n { |
| n = m |
| } |
| |
| // Apply replacements to buffer. |
| var b Builder |
| b.Grow(len(s) + n*(len(new)-len(old))) |
| start := 0 |
| for i := 0; i < n; i++ { |
| j := start |
| if len(old) == 0 { |
| if i > 0 { |
| _, wid := utf8.DecodeRuneInString(s[start:]) |
| j += wid |
| } |
| } else { |
| j += Index(s[start:], old) |
| } |
| b.WriteString(s[start:j]) |
| b.WriteString(new) |
| start = j + len(old) |
| } |
| b.WriteString(s[start:]) |
| return b.String() |
| } |
| |
| // ReplaceAll returns a copy of the string s with all |
| // non-overlapping instances of old replaced by new. |
| // If old is empty, it matches at the beginning of the string |
| // and after each UTF-8 sequence, yielding up to k+1 replacements |
| // for a k-rune string. |
| func ReplaceAll(s, old, new string) string { |
| return Replace(s, old, new, -1) |
| } |
| |
| // EqualFold reports whether s and t, interpreted as UTF-8 strings, |
| // are equal under simple Unicode case-folding, which is a more general |
| // form of case-insensitivity. |
| func EqualFold(s, t string) bool { |
| // ASCII fast path |
| i := 0 |
| for ; i < len(s) && i < len(t); i++ { |
| sr := s[i] |
| tr := t[i] |
| if sr|tr >= utf8.RuneSelf { |
| goto hasUnicode |
| } |
| |
| // Easy case. |
| if tr == sr { |
| continue |
| } |
| |
| // Make sr < tr to simplify what follows. |
| if tr < sr { |
| tr, sr = sr, tr |
| } |
| // ASCII only, sr/tr must be upper/lower case |
| if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' { |
| continue |
| } |
| return false |
| } |
| // Check if we've exhausted both strings. |
| return len(s) == len(t) |
| |
| hasUnicode: |
| s = s[i:] |
| t = t[i:] |
| for _, sr := range s { |
| // If t is exhausted the strings are not equal. |
| if len(t) == 0 { |
| return false |
| } |
| |
| // Extract first rune from second string. |
| var tr rune |
| if t[0] < utf8.RuneSelf { |
| tr, t = rune(t[0]), t[1:] |
| } else { |
| r, size := utf8.DecodeRuneInString(t) |
| tr, t = r, t[size:] |
| } |
| |
| // If they match, keep going; if not, return false. |
| |
| // Easy case. |
| if tr == sr { |
| continue |
| } |
| |
| // Make sr < tr to simplify what follows. |
| if tr < sr { |
| tr, sr = sr, tr |
| } |
| // Fast check for ASCII. |
| if tr < utf8.RuneSelf { |
| // ASCII only, sr/tr must be upper/lower case |
| if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' { |
| continue |
| } |
| return false |
| } |
| |
| // General case. SimpleFold(x) returns the next equivalent rune > x |
| // or wraps around to smaller values. |
| r := unicode.SimpleFold(sr) |
| for r != sr && r < tr { |
| r = unicode.SimpleFold(r) |
| } |
| if r == tr { |
| continue |
| } |
| return false |
| } |
| |
| // First string is empty, so check if the second one is also empty. |
| return len(t) == 0 |
| } |
| |
| // Index returns the index of the first instance of substr in s, or -1 if substr is not present in s. |
| func Index(s, substr string) int { |
| n := len(substr) |
| switch { |
| case n == 0: |
| return 0 |
| case n == 1: |
| return IndexByte(s, substr[0]) |
| case n == len(s): |
| if substr == s { |
| return 0 |
| } |
| return -1 |
| case n > len(s): |
| return -1 |
| case n <= bytealg.MaxLen: |
| // Use brute force when s and substr both are small |
| if len(s) <= bytealg.MaxBruteForce { |
| return bytealg.IndexString(s, substr) |
| } |
| c0 := substr[0] |
| c1 := substr[1] |
| i := 0 |
| t := len(s) - n + 1 |
| fails := 0 |
| for i < t { |
| if s[i] != c0 { |
| // IndexByte is faster than bytealg.IndexString, so use it as long as |
| // we're not getting lots of false positives. |
| o := IndexByte(s[i+1:t], c0) |
| if o < 0 { |
| return -1 |
| } |
| i += o + 1 |
| } |
| if s[i+1] == c1 && s[i:i+n] == substr { |
| return i |
| } |
| fails++ |
| i++ |
| // Switch to bytealg.IndexString when IndexByte produces too many false positives. |
| if fails > bytealg.Cutover(i) { |
| r := bytealg.IndexString(s[i:], substr) |
| if r >= 0 { |
| return r + i |
| } |
| return -1 |
| } |
| } |
| return -1 |
| } |
| c0 := substr[0] |
| c1 := substr[1] |
| i := 0 |
| t := len(s) - n + 1 |
| fails := 0 |
| for i < t { |
| if s[i] != c0 { |
| o := IndexByte(s[i+1:t], c0) |
| if o < 0 { |
| return -1 |
| } |
| i += o + 1 |
| } |
| if s[i+1] == c1 && s[i:i+n] == substr { |
| return i |
| } |
| i++ |
| fails++ |
| if fails >= 4+i>>4 && i < t { |
| // See comment in ../bytes/bytes.go. |
| j := bytealg.IndexRabinKarp(s[i:], substr) |
| if j < 0 { |
| return -1 |
| } |
| return i + j |
| } |
| } |
| return -1 |
| } |
| |
| // Cut slices s around the first instance of sep, |
| // returning the text before and after sep. |
| // The found result reports whether sep appears in s. |
| // If sep does not appear in s, cut returns s, "", false. |
| func Cut(s, sep string) (before, after string, found bool) { |
| if i := Index(s, sep); i >= 0 { |
| return s[:i], s[i+len(sep):], true |
| } |
| return s, "", false |
| } |
| |
| // CutPrefix returns s without the provided leading prefix string |
| // and reports whether it found the prefix. |
| // If s doesn't start with prefix, CutPrefix returns s, false. |
| // If prefix is the empty string, CutPrefix returns s, true. |
| func CutPrefix(s, prefix string) (after string, found bool) { |
| if !HasPrefix(s, prefix) { |
| return s, false |
| } |
| return s[len(prefix):], true |
| } |
| |
| // CutSuffix returns s without the provided ending suffix string |
| // and reports whether it found the suffix. |
| // If s doesn't end with suffix, CutSuffix returns s, false. |
| // If suffix is the empty string, CutSuffix returns s, true. |
| func CutSuffix(s, suffix string) (before string, found bool) { |
| if !HasSuffix(s, suffix) { |
| return s, false |
| } |
| return s[:len(s)-len(suffix)], true |
| } |